There is an affinity between the refrigerants and lubricants used in refrigeration systems. As a result, it is normal for some refrigerant to be present in the oil and for some oil to be present in the refrigerant. When the hermetic compressor is shut off, refrigerant in the system tends to migrate and condense. Since the compressor is often at a low point in the system there is a tendency for the refrigerant to collect there diluting the oil in the sump and posing the risk of a flooded start due to the presence of liquid refrigerant. Crankcase heaters are designed to keep refrigerant from migrating into the crankcase or sump of a hermetic compressor during an off cycle. The crankcase heaters are normally energized continuously even though they are only effective part of the time.